Numerical modelling of the thermospheric heat budget

Abstract

Numerical models of the thermal budget of the earth's upper atmosphere in the height range of 90–500 km are developed. The main sources and sinks of energy, including infrared radiative cooling in vibrational‐rotational bands of NO, CO 2 , OH, and O 3 as well as heating and cooling arising from dissipation of turbulent energy and eddy heat transport, are taken into account. The calculated temperature and density height profiles are in good agreement with the respective profiles from the Cira (1972) and Jacchia (1977) models. It is found that thermal collisions between CO 2 and atomic oxygen play an important role in the formation of the lower thermospheric 15µ radiation. It is also found that the maximum value of the time average eddy diffusion coefficient in the thermosphere cannot exceed 3×10 6 cm²s −1 . The calculations show that for the statistically average thermospheric condition infrared radiative cooling by CO 2 and NO in the 15µ and 5.3µ bands, but not eddy turbulence or molecular conduction provides the major loss of heat in the height range of 90–180 km.